1. Field of the Invention
The present invention relates to a power steering for a wheeled vehicle and more specifically to an electrically driven power steering for an industrial vehicle such as a fork lift or the like which is operated on electrical power and which is subject to high loads.
2. Description of the Prior Art
Japanese Patent Application Provisional Publication 60-226359 discloses a power steering arrangement wherein an electric motor is disposed between the main steering shaft and the output shaft. One end of the driven shaft of the motor is connected to the main steering shaft through a deformable elastomeric member while the other end is connected to the output shaft through a gearing. A sensor is disposed in the elastomeric member and arranged to output a signal indicative of a torque being applied to the steering wheel or the like operatively connected with the steering main shaft.
The motor control circuit includes a battery, a key switch circuited with the steering sensor and a relay. This relay serves to connect the motor with the battery when closed.
However, this arrangement has suffered from the drawback that when the wheels are steered a low speeds or standstill for example, the elastomeric material of the tires is distorted. Thus, in the event that if driver is still in the process of steering the wheels of the vehicle by rotating the steering wheel at the time the power to the motor is cut off by the opening of any relay, the distortion in the tires induced by the operation of the motor, acts a spring and a reverse torque is suddenly applied back through the shafts and elastomeric member to the steering wheel producing a strong and unpleasant kickback.